The measurement of ambient atmospheric pressure (commonly referred to as static pressure) has, in the past, been accomplished with the acceptable results falling within a wide range of allowable tolerances. However, in recent years, the necessity of obtaining an accurate ambient atmospheric pressure reading has increased due to certain industrial conditions that now exist. For instance, in pharmaceutical plants where an internal pressure greater than that of the outside must be maintained in order to avoid contamination, a reliable method of monitoring the differential pressure must be used. Conversely, when nuclear material is to be used within an industrial complex, the internal pressure must be maintained at a lower level than that of the outside atmosphere. This particular pressure differential will prevent any nuclear contamination from escaping into the outside atmosphere.
The measurement of internal pressure is a relatively simple task due mainly to the fact that air currents within a building are usually low enough to permit accurate readings. However, in order to evaluate and measure the true static ambient atmospheric pressure which exists exteriorly of the building, it it important to take steps which negate the effects of wind velocity.
The most commonly used exterior probe has usually been a vertically extended pipe having its uppermost end open to the atmosphere and its lowermost end communicatively connected to a pressure sensing device. It is to be appreciated that this method could produce an erroneous static air pressure value, due mainly to adverse effects caused by nonhorizontal air movement across the exterior probe and other factors influencing dynamic static pressure.